Proj and invproj perform respective forward and inverse transformation
of cartographic data to or from Cartesian data with a wide range of
selectable projection functions (over 100 projections).

Geod and invgeod perform geodesic (Great Circle) computations for
determining latitude, longitude and back azimuth of a terminus point
given a initial point latitude, longitude, azimuth and distance
(direct) or the forward and back azimuths and distance between an
initial and terminus point latitudes and longitudes (inverse).

The proj package now provides builtin datum conversion.
